problem with `opam init`

I tried to get opam running on my Ubuntu laptop. After downloading
the 0.6.0 tarball from the OcamlPro tutorial page
(http://opam.ocamlpro.com/doc/Tutorial.html) and building and
installing it without incident, my first opam command fell over:

I suspect the repository version may have moved beyond 0.6.0 as things are
rapidly being fixed (or it could be something else). Hopefully this aspect
will stabilise soon, before it goes into a public beta.